The Condon arrangement provides two separate essentially matching toroidal magnetic cores with line circuit windings, control circuit windings, sense windings, and feedback windings. Line current flowing in the line windings causes in the two cores essentially equal amounts of the same polarity of line current magnetizing intensity H. A pulse of control current flowing in the control windings causes corresponding changes in the two cores of control current H where the changes of control H in the two cores are of essentially equal amounts of control H but of the opposite polarity. Each change of control H causes the magnetic inductions B in the two cores to undergo corresponding changes from an amount of one polarity of B corresponding to a zero amount of control H to B saturation of the same polarity of B and then from B saturation back to an amount of the same polarity of B corresponding to a zero amount of control H. These changes of B in the two cores occur along minor saturation hysteresis loops. The changes of B in the two cores produce induced voltages in the sense windings which are connected in series oppositon with regard to polarity of the induced voltages. With no line H present in the two cores, the output of the series connection of sense windings is essentially zero voltage since the changes of B in the two cores are essentially of equal amounts of opposite polarity. The presence in the two cores of line H, due to the flow of line current, causes the changes of B in the two cores to differ by an amount which is a measure of the amount and polarity of line H (and thus a measure of the amplitude and polarity of line current). Such a difference in the changes of B in the two cores produces a voltage pulse, the amplitude and polarity and duration of which are a measure of the difference between the amounts and polarities of the changes of B in the two cores. A succession of voltage pulses is cumulatively and algebraically integrated to provide a changing output voltage, the amplitude and polarity of which are a measure of the cumulative integation. The output voltage is used to cause in each core, by means of either the sense windings or the feedback windings, an amount of feedback H where the amount is according to the output voltage and the polarity opposes any line H in the two cores. The output voltage becomes essentially constant when the feedback H essentially cancels the line H in the two cores; and, the amplitude and polarity of the constant output voltage are a measure of the amplitude and polarity of line current.
While the Condon arrangement is quite satisfactory from an operational standpoint, it uses at least three sets of core windings to effect the three functions of line current coupling, control current pulse coupling, and sense voltage coupling. In one Condon arrangement the sense windings are used to effect the feedback function; whereas, in another Condon arrangement, a fourth set of core windings is used to effect the feedback function. It is considered advantageous to simplify the core winding situation in order not only to reduce costs but also to reduce the number and complexity of circuit and magnetic structure design considerations.